Coupler microwave-activated controlled phase gate on fluxonium qubits

Abstract

Tunable couplers have recently become one of the most powerful tools for implementing two-qubit gates between superconducting qubits. A tunable coupler typically includes a nonlinear element, such as a SQUID, which is used to tune the resonance frequency of an LC circuit connecting two qubits. Here we propose a complimentary approach where instead of tuning the resonance frequency of the tunable coupler by applying a quasistatic control signal, we excite by microwave the degree of freedom associated with the coupler itself. Due to strong effective longitudinal coupling between the coupler and the qubits, the frequency of this transition strongly depends on the computational state, leading to different phase accumulations in different states. Using this method, we experimentally demonstrate a CZ gate of 44 ns duration on a fluxonium-based quantum processor, obtaining a fidelity of $97.6\pm 0.4\%$ characterized by cross-entropy benchmarking.

arXiv comment8 pages, 7 figures, 1 table

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Cited by in corpus (8)

• Native approach to controlled-Z gates in inductively coupled fluxonium qubits
• High coherence fluxonium manufactured with a wafer-scale uniformity process
• High-precision pulse calibration of tunable couplers for high-fidelity two-qubit gates in superconducting quantum processors
• Single-Qubit Gates Beyond the Rotating-Wave Approximation for Strongly Anharmonic Low-Frequency Qubits
• Fast microwave-driven two-qubit gates between fluxonium qubits with a transmon coupler
• Effect of Etching Methods on Dielectric Losses in Transmons
• Transmon-assisted high-fidelity controlled-Z gates for integer fluxonium qubits
• Resource-efficient shadow tomography using equatorial stabilizer measurements